Knowledge Check • The Blood Project

True of false: the following is the current diagnostic criteria for polycythemia vera.

a

True

b

False

These are the criteria from WHO 2008.

What is the major difference between 2008 and 2016 WHO criteria?

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A relaxation of the Hb/Hct threshold to pick up masked PV

Type	WHO 2008	WHO 2016

Major	Hb > 18.5 M, Hb > 16.5 F or other evidence of increased red cell volume	Hb > 16.5 M, Hb > 16.0 F, Hct >49% M, Hct > 48% F or other evidence of increased red cell volume
	Presence of JAK2 V617F or other functionally similar mutation such as JAK2 exon 12 mutation	Presence of JAK2V617F or JAK2 exon 12 mutation
	N/A	BM biopsy showing hypercellularity for age with trilineage growth (panmyelosis) including prominent erythroid, granulocytic, and megakaryocytic proliferation with pleomorphic, mature megakaryocytes (differences in size)
Minor	Serum erythropoietin level below the reference range for normal	Subnormal serum erythropoietin level
	Endogenous erythroid colony formation in vitro
	Bone marrow biopsy showing hypercellularity for age with trilineage growth (panmyelosis) with prominent erythroid, granulocytic, and megakaryocytic proliferation
Diagnosis	Diagnosis of PV requires the presence of both major criteria and one minor criterion or the presence of the first major criterion together with two minor criteria	Diagnosis of PV requires meeting either all 3 major criteria, or the first 2 major criteria and the minor criterion*

A comparison of the WHO 2008 and 2016 diagnostic criteria for polycythemia vera (PV). the major differences are highlighted in bold red. First, the threshold for Hb/Hct has been lowered so that patients with masked PV are more likely to be diagnosed. Second, bone marrow biopsy is a minor criterion in the 2008 panel, but a major criterion in 2016. However, the 2016 diagnostic criteria note that bone marrow biopsy may not be required in those with hemoglobin levels >18.5 g/dL in men (hematocrit, 55.5%) or >16.5 g/dL in women (hematocrit, 49.5%) Finally, the 2016 criteria do not include endogenous erythroid colony formation in vivo. *Criterion number 2 (BM biopsy) may not be required in cases with sustained absolute erythrocytosis: hemoglobin levels >18.5 g/dL in men (hematocrit, 55.5%) or >16.5 g/dL in women (hematocrit, 49.5%) if major criterion 3 and the minor criterion are present. However, initial myelofibrosis (present in up to 20% of patients) can only be detected by performing a BM biopsy; this finding may predict a more rapid progression to overt myelofibrosis (post-PV MF).

Sort the parameters (top) according to the appropriate 2016 PV diagnostic criteria buckets (bottom):

Hb>16.5 (M)/16.0 (F)

BM biopsy

Hb>18.5 (M)/18.0 (F)

JAK2V617F

Elevated LDH

Hct>49 (M)/48% (F)

Endogenous erythroid colony formation in vitro

CALR mutation

Subnormal serum erythropoietin level

Minor crirteria

Major criteria

Not a criterion

Consider the following patients:

Type	Patient 1 (male)	Patient 2 (female)	Patient 3 (male)	Patient 4 (female)
Hb	16.3 g/dL	21 g/dL	17 g/dL	17.5 g/dL
JAK2 V617F	Positive	Negative	Positive	Not done
BM biopsy	Not done	Not done	Not done	Consistent with PV
Serum erythropoietin level	Low	Normal	Low	Low

Which of these patient(s) meets the WHO 2016 diagnostic criteria for polycythemia vera?

a

Patient 1

Requires bone marrow biopsy

b

Patient 2

c

Patient 3

d

Patient 4

True or false: the white cell count and platelet count may be elevated in patients with polycythemia vera, but are not part of the diagnostic criteria:

a

True

b

False